Adding subtitles / closed captions to a video lesson on Calibrae is easy. It takes two steps.
Create a Web Video Text Track file (VTT) with the narrative text for each language. There are many good free and paid tools that can be used to create VTT files. Subtitle Edit Online is a reasonable option. It is free, web-based (but does not require video upload), is fairly intuitive, and outputs a standard VTT file that can be uploaded to Calibrae.
The exported VTT file is a text file with timestamps. The VTT file is now ready for upload to Calibrae.
NOTE: Any good VTT editor will output the same format VTT file. Go ahead and use the VTT tool of your choice.
Repeati the process to create VTT files for each of your required languages.
With a VTT file created, navigate to the edit page of the video activity, then...
Repeat the process with the VTT file of each language.
Finally, switching to the learner view, the learner can now select to view any of the Closed Caption subtitles.